as observed Ml the Tongue of the living Frog, Toad, fyc. 279 



tain that the secretion which lubrifies the surface of the tongue 

 is very abundant over these bodies, and that it appears to arise 

 from them. On examining the fluid, it was found to be a 

 thick mucus, without any of the globules commonly known to 

 characterize it. 



The tongue of the toad presents likewise numerous papillie 

 and glands similar to those of the frog. In addition, nume- 

 rous depressions in the mucous membrane are frequently 

 seen, which are of the same nature as the mucous follicles or 

 crypts in man. Around them and on their exterior we find 

 a very abundant network of capillaries. 



Vascular System and Circulation. — Having examined the 

 glands, which may be considered as appendages of the vas- 

 cular system, I now proceed to describe other phaenomena of 

 the same system, as observed in its general distribution 

 throughout the tongue. The blood, we are aware, consists 

 of a transparent fluid holding in suspension numerous par- 

 ticles, most of which are red and of a flattened shape, while a 

 few others are colourless, and spherical in form. The various 

 movements and appearances presented by these particles in 

 their circuit from the arteries to the veins, constitute the prin- 

 cipal phasnomena to be observed by the microscope. The 

 tongue offers great facility for observing the two opposite 

 currents in the veins and arteries, as they run together side 

 by side for a considerable distance in that organ. 



I have already mentioned the rapid injection of the tongue 

 as soon as it is subjected to the experiment, from the irritation 

 caused by extracting it from the mouth. The degree of ra- 

 pidity with which this takes place varies in different subjects, 

 even when they are selected as similar as possible with regard 

 to age, size, &c. These varieties are to be attributed to cer- 

 tain constitutional differences or idiosyncrasies, such as we find 

 in human beings, and which are found to exist in a minor 

 degree throughout the animal kingdom, and are inseparable 

 from animal life. While preparing the tongue, we find like- 

 wise some of these constitutional peculiarities; for in some 

 subjects it may be expanded without the least laceration, 

 while in others it is extremely liable to tear with the slightest 

 force used. In proportion as we penetrate more closely into 

 the structure of this organ, we find numerous peculiarities of 

 structure referable to the same cause; but particularly when 

 examining the changes which occur in the vascular system, 

 these evidences of constitutional peculiarities are more appa- 

 rent. As this point is intimately connected with the vital 

 functions, and may lead us to a better acquaintance with the 

 laws by which they are governed, it is unnecessary to point 

 out the interest with which it deserves to be examined. 



